Tropical to subtropical
circulation
Major Zones
• ITCZ (Intertropical convergence zone)
• Subtropics (30 degrees, north/south
hemisphere)
• Front
• Poles
Hadley Cells
• Giant tropical circulation pattern
• Partially driven by convective processes
along the ITCZ
Hadley Cell Products
• Heavy rainfall with in the ITCZ
• Major transfer of energy from the ITCZ to
higher latitudes
– Sensible heat
– Latent heat
• Sets the stage for the dominant pressure
cells in the Earth’s atmosphere
Pressure Cells
• ITCZ
– Rising hot air
– Creates zones of low pressure
• Subtropics
– Sinking dry air
– Creates zones of High pressure
Hadley Cell products continued
• Subtropics: ↓ condensation and 
evaporation
– Sahara dessert
Subtropics feed into the Hadley cell
• Warm dry air (trade winds, N & S) moves
through the subtropics and towards the
tropics picking water vapor.
• These warm moist winds meet in the ITCZ
and feed the Hadley cell.
The Sun’s role
• Provides energy to the Hadley cell
• So, if the energy from the sun changes so
does the strength of the Hadley cell and
the location of the ITCZ
– Summer, N (June-September), ITCZ shifts
north
– Summer, S (December-March), ITCZ shifts
south
Monsoons
Monsoon circulation
Atmospheric circulation at middle
and high latitudes
Atmospheric circulation at middle
and high latitudes
• The movement of air from mid to high
latitudes
• Areas above 35 degrees latitude
• Air typically moves from areas of high
pressure to areas of low pressure
• Except……..
Effects on the land in mid latitudes
• Low pressure cells tend to move fast in a
west to east direction in the mid-latitudes
• Sometimes these cells are forced to move
over topographically high areas.
– Orographic precipitation